Often it is desirable to obtain substances in their elemental forms or high quality alloys of these substances in order to use them in certain high-end applications, for example, sports and leisure activities. However, in nature most substances are not readily accessible in their elemental forms.
For example, frequently titanium occurs in ores as a dioxide or mixed oxide with iron. Because of titanium's affinity for gases and most metals in the periodic table, it is quite difficult to extract elemental titanium from its ores. Consequently, in order to obtain elemental Ti, complex and now well-known processes have been developed. Unfortunately, these processes, as well as similar processes for obtaining other elemental materials can be cumbersome and costly.
Many naturally occurring substances either exist as halides or are easily converted into halides. These halides may be reduced to their elemental forms by any one of a number of well-known processes. For example, titanium tetrachloride (TiCl4) may be reduced to Ti through the use of reducing agents such as hydrogen, carbon, sodium, calcium, aluminum or magnesium.
Methods for reducing halides in order to obtain elemental materials have been developed for both batch and continuous processes. One example of a method for the reduction of a precursor material in a batch process is the magnesium reduction of titanium tetrachloride to produce elemental titanium. Unfortunately, the product of this type of batch process requires significant material handling, which provides opportunities for contamination and variation in quality from batch to batch. Consequently, a significant amount of effort has been directed toward developing continuous reduction processes.
Several different continuous processes for producing elemental materials have been developed. For example, it is known to use Na to reduce TiCl4 to Ti powder at a temperature of between 350 and 800° C. This process can efficiently produce Ti powder from TiCl4 at a reasonable cost. Thus, it has high commercialization potential. However, the product Ti powder has a relatively high oxygen concentration, which causes powder sintering. Further, in this process there is an undesirable cumbersome step of separating the Ti powder from Na. Still further, Na can be costly, is of limited supply and must be handled carefully.
Another method for reduction of a precursor material, for example, for the production of titanium, uses plasma technology to change the thermodynamics of the elemental Ti formation by vaporizing and ionizing it. However, due to the high melting temperature of titanium metal, most plasmas operate at temperatures of above 4000° C. Therefore, the high energy consumption and the limited refractory material availability render this process expensive.
Another known method involves the use of an electron beam to produce Ti powder. This process is conceptually similar to a plasma process, that is, by utilizing the high temperature from an electron beam, one may produce Ti powder. Unfortunately, this process also consumes a great deal of energy and can be costly.
Still another known method uses mechanochemical technology to produce Ti powder. In this process, TiO2/TiCl4 and CaH/MgH are first milled to produce TiH+CaO/CaCl2 at temperatures from room temperature to 700° C. Then, TiH is annealed in a vacuum to produce Ti powder. This process is still in the early stage relative to industrial utilization, and thus far, it appears that the products of this method may suffer from being impure and having slow reaction rates.
In addition to these processes, it has long been known to produce spongy Ti by electrolysis of TiO2 in a fused salt bath. In one known process, TiO2 is directly electrolyzed in fused CaCl2 at approximately 950° C. to produce a Ti sponge, and the sponge is converted to a powder. Unfortunately, due to the limitations of current technology, it is difficult, if not impossible, to avoid oxygen contamination on the product since the Ti sponge is produced on the surface of TiO2.
The aforementioned methods all suffer from being unable to produce sufficiently pure elemental materials in a sufficiently economical manner. Because of the limitations of these methods, the ability to produce high quality alloys containing these elemental materials is also limited. The present invention provides a solution to these problems by providing methods for economically producing sufficiently high quality elemental materials and alloys.